Maleated poly(propylene carbonate)/calcium stearate (MAPPC/CaSt(2)) composite was prepared through melt-extruding poly(propylene carbonate) (PPC) with maleic anhydride and CaSt(2). The processability, thermal stability, interaction between two components as well as the morphology of the composites were systematically characterized. The flow instability of biodegradable PPC was greatly alleviated due to the incorporation of stearate additive in polymer matrix. It was found that the MAPPC and MAPPC/CaSt(2) composites were more thermostable than pristine PPC under melt-processing conditions. The melt fluidity of the composites was noticeably superior to that of MAPPC, arising from the lubricating effect of CaSt2 on the polymer/barrel wall interface as well as from the improvement of resistance to thermal degradation of the composite. The coordination interaction between MAPPC and calcium ion also contributes to the enhanced thermal stability and high melt stability of composites. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 692-700, 2011